modded track fps problem

[janaucarre]

Hi,
These two last evenings i began building a new track using race track builder.
I import it in 3dsmax and re-apply the textures to the road and the map.
I create the misc with tracked and try in game.
At some points the fps drop down about 5-10 fps and near the and to 0fps.
The track is about 8km long and there is only the road and the map, so two textures are used.

Someone has an idea from where the problem is coming?
I build in the past a track more than 15km long with many textures and mountain and other 3d objects without any problem and more than 500'000 polygons.
The actual track is about 200'000 polygons.

Thank you in advance for all your help.